Magnesium hydroxide

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Teratogenicity study of magnesium chloride hexahydrate in rats

Author:

Usami M. et al.

Year:

1996

Bibliographic source:

Eisi Shikenjo Hokoku [Bulletin of National Institute of Hygienic Sciences] 1996; 114: 16-20

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Magnesium chloride hexahydrate

EC Number:

616-575-1

Cas Number:

7791-18-6

IUPAC Name:

Magnesium chloride hexahydrate

Specific details on test material used for the study:

- Name of test material: Magnesium chloride hexahydrate
- Molecular formula: MgCl:6H20
- Molecular weight: 203.30
- Analytical purity: 95% due to its being used as a food additive.
- Description: Colourless to white crystal

Test animals

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Japan
- Age at study initiation: Female (10 weeks old) male (11 weeks old)
- Housing: Pregnant rats were kept in aluminum cages through the test period.
- Diet: Freely consume solid food (oriental yeast0
- Water: Tap water

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Pregnant rats were kept at a set temperature of 25 ±2 °C.
- Humidity (%):55 ± 5%
- Air changes (per hr):15 cycles/hr
- Photoperiod (hrs dark / hrs light): Lighted at 12-hour intervals (period of light: 6:00 to 18:00)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

Nulliparous females spent the night with males, then the next morning the rats were tested for pregnancy by checking if any sperm was in their vaginas. Gestation days were tabulated by setting the day on which the sperm was found as gestation day 0.

Duration of treatment / exposure:

Day 6 to day 15 of pregnancy

Frequency of treatment:

Once a day

Duration of test:

Day 6 to day 20 of pregnancy

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

200 mg/kg bw/day

Remarks:

actual ingested with doses based on the body weight at day 6 of gestation.

Doses / concentrations 3

Dose / conc.:

400 mg/kg bw/day

Remarks:

actual ingested with doses based on the body weight at day 6 of gestation.

Doses / concentrations 4

Dose / conc.:

800 mg/kg bw/day

Remarks:

actual ingested with doses based on the body weight at day 6 of gestation.

No. of animals per sex per dose:

22

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale: When setting dosage levels, doses of 0, 250, 500 and 1000 mg/kg/day and one group of 4 rats in a preliminary study were used. As a result, sedation, decreased body temperature, salivation, and watery stool were observed, while 2 rats died. No effects of Magnesium chloride hexahydrate were observed in the reproduction of surviving rats. Considering these results, in terms of group composition, 3 dosage levels of 200, 400 and 800 mg/kg/day were established to be administered to 3 magnesium chloride hexahydrate treatment groups.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATION: YES
The general condition of the animals was observed every day.

BODYWEIGHT: Yes
Body weight was measured at day 0, 1, 3, 6, 9, 12, 15, and 17 of pregnancy.

FOOD INTAKE: YES
Food intake was measured at day 0, 1, 3, 6, 9, 12, 15, and 17 of pregnancy.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: The pregnant rats were slaughtered on gestation day 20 and the number of corpora lutea, the number of implants, and the number of dead implants were examined.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes: the exterior of live fetuses was examined for abnormalities and sex, then body weight was measured.
- Internal organ examinations: Yes: The internal organs of approximately one-half of the live fetuses were observed. In observing the internal organs, the macrosection technique was used for the cephalic and abdominal regions, and the microdissection technique for the thoracic region.
- Skeletal examinations: Yes: A sample of Alizarin red S-stained skeletal preparation was made for approximately one-half of the live fetuses.
- Head examinations: Yes half per litter (according to a gross sectioning technique)

Statistics:

Either pregnant rats or litters were used as units of calculation. For tests with a significant difference between the control group and the magnesium chloride hexahydrate treatment groups, the Fisher direct method for frequency data was used. For quantitative data, after using the Bartlett homoscedastic test to determine whether there was a difference in variance between groups, variance analysis and the Scheffe method were then used. For quantitative data and enumerative data with an observed difference in variance between groups, the Kruskal-Wallis test and the Scheffe method were used.

Indices:

no data

Historical control data:

no data

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

not specified

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

not specified

Changes in number of pregnant:

no effects observed

Details on maternal toxic effects:

There were no differences between the groups with regard to general condition and death. Furthermore, no significant differences between the control group and magnesium chloride hexahydrate groups were observed with respect to body weight and food consumption. Regarding the number of corpora lutea, number of implants, number of living fetuses, sex ratio, fetal weight and mortality of implants/fetuses, no significant differences between control group and the magnesium chloride hexahydrate groups were observed.

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

> 800 mg/kg bw/day

Based on:

test mat.

Remarks on result:

other: no effects at highest tested dose

Results (fetuses)

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

not specified

Anogenital distance of all rodent fetuses:

not specified

Changes in postnatal survival:

not specified

External malformations:

effects observed, non-treatment-related

Description (incidence and severity):

One to 4 fetuses with gross malformations were found in each group. However, regarding the incidence rate, there was no significant difference between control group and magnesium chloride hexahydrate groups.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

In the 800 mg/kg/day group, one fetus had skeleton malformations, however, with regard to the incidence rate; there was no significant difference between control group and the magnesium chloride hexahydrate groups. Furthermore, no significant differences between control group and magnesium chloride hexahydrate groups were observed as far as the incidence rate of skeletal variations is concerned. Regarding the incidence rate of fetuses with lumbar rib and additional rib bones, there were no significant differences. No significant differences were found in the number of ossification centers, metacarpal and metatarsal bones as well as sacral and tail vertebrae. The aforementioned numbers were examined as indicators for the progress of ossification.Four to 6 fetuses in each group showed malformations, however, no significant difference were observed between control group and magnesium chloride hexahydrate groups.

Visceral malformations:

not specified

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

> 800 other: mg/kg/day

Basis for effect level:

other: no observed adverse effects at highest tested dose

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

No increased incidences of foetal malformation were noted, and no toxic signs were found in the pregnant rats and the foetuses.

Table 1. Fetal growth in pregnant rats treated with magnesium chloride hexahydrate

Dose (mg/kg/day)		0 (Control)	200	400	800
No. of litters		22	22	22	22
No. of corpora lutea		373	370	361	362
No. of implants		364	340	345	345
No. of live foetuses		346	326	324	332
Foetal weight (g)	Male	3.95	3.98	3.87	3.98
	Female	3.73	3.75	3.72	3.81
No. of dead implants		18	14	21	13
Mortality (%)		4.8	4.8	5.9	3.6

 

Table 2. Gross malformations in the foetuses from pregnant rats treated with magnesium chloride hexahydrate

Dose (mg/kg/day)	0 (Control)	200	400	800
No. of litters	22	22	22	22
No. foetuses examined	346	326	324	332
No. of litters with malformed foetuses	3	1	3	1
No. of foetuses with malformation	3	1	4	1

 

Applicant's summary and conclusion

Conclusions:

In conclusion, magnesium chloride hexahydrate has no teratogenicity in rats when given by gavage at the doses examined in this study. The no observed adverse effect level for magnesium chloride hexahydrate was determined to be >800 mg/kg/day for both pregnant rats and rat fetuses.

Executive summary:

In a publication from Usami et al., teratogenicity of magnesium chloride hexahydrate was examined in rats. 22 male and female Wistar rats were orally treated with magnesium chloride hexahydrate (>95% purity) in water at doses of 0, 200, 400 and 800 mg/kg bw/day from Day 6 to Day 15 of pregnancy. The pregnant rats were sacrificed on day 20 of pregnancy and their fetuses were examined for malformation. It was found that magnesium chloride hexahydrate caused no increased incidences of fetal malformation and no toxic signs in the pregnant rats and the fetuses. Even a dose of 800 mg/kg bw/day, considered the maximum non-fatal dose of magnesium chloride hexahydrate in pregnant rats, did not increase the incidence of teratogenicity. The no observed adverse effect level for magnesium chloride hexahydrate was determined to be >800 mg/kg/day for both pregnant rats and rat fetuses, which is equal to 230 mg/kg bw/day magnesium hydroxide.